Implement the "First-Party-Only" cookie attribute.

First-party-only cookies allow servers to mitigate the risk of cross-site
request forgery and related information leakage attacks by asserting that a
particular cookie should only be sent in a "first-party" context.

This patch adds support for the 'First-Party-Only' attribute to the
CookieMonster and CookieStore, but does not yet wire up requests such that
the flag has any effect. https://codereview.chromium.org/940373002 will do so
by correctly setting the first-party URL on the CookieOptions object used to
load cookies for a request.

Spec: https://tools.ietf.org/html/draft-west-first-party-cookies

Intent to Implement: https://groups.google.com/a/chromium.org/d/msg/blink-dev/vT98riFhhT0/3Q-lADqsh0UJ

BUG=459154
TBR=dpolukhin@chromium.org

Review URL: https://codereview.chromium.org/876973003

Cr-Commit-Position: refs/heads/master@{#317544}
23 files changed